Communication devices such as terminals are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or mobile stations. Terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two terminals, between a terminal and a regular telephone and/or between a terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Terminals may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which may be divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
Some of the current standardization procedures are focused on providing for standards for low cost UEs. In agreement with this, the objective of the 3GPP Release (Rel)-12 work item on “Low cost & enhanced coverage Machine-Type Communications (MTC) UE for LTE” is to specify a new low complexity UE type with the following complexity reduction techniques: a) Single receive antenna, b) DL and UL maximum Transport Block Size (TBS) of 1000 bits, and c) Half duplex operation, optional.
Because such a low complexity UE may have restrictions in its operation, such as the TBS restriction just mentioned, it may need to inform the network, e.g., its serving network node, of its capability/ies. In the particular context of the Radio Resource Control (RRC) procedure, the existing working assumption is that the UE does not indicate its low complexity capability in Msg1, Preamble, nor in the Radio Resource Control (RRC) context of Msg3-RRCConnectionRequest- or Msg5-RRCConnectionSetupComplete-.
A low complexity UE supporting only 1000 bit UL TBS may restrict its Buffer Status Report (BSR), a Medium Access Control (MAC) control element, to less than 1000 bit until having provided the UE capabilities to the eNB or having received the first RRCConnectionReconfiguration message, so that the network may restrict all UL grants accordingly.
Once the network is informed that the UE is a low complexity UE, it may be possible for the UE to report a value greater than 1000 bit if there is data in the buffers even though the network may restrict the UL grants accordingly. This is because a low complexity UE may have more than 1000 bits in the buffer, even if it may only send/receive up to 1000 bits at a time.
However, under the current working assumption, a UE with restrictions in its operation may still receive grants it may not handle, and experience a communication failure.